Radiation Therapy System

Abstract

To provide a radiotherapy system capable of shortening a time required for re-planning of an adaptive treatment more than before.SOLUTION: A radiotherapy system 1 for emitting radiation performs first calculation that creates a new image on the basis of on an image during treatment planning and another image newer than the image during the treatment planning, performs second calculation creating a target dose distribution on the basis of the image during the treatment planning, a dose distribution, and the another image newer than the image during the treatment planning, and optimizes an irradiation parameter with the target dose distribution as a target.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a radiotherapy system that treats an affected area such as a tumor by irradiating it with radiation such as particle beams. [Background technology]

[0002] There are known methods of irradiating patients with cancer and other conditions with radiation such as particle beams and X-rays. Particle beams include proton beams and carbon ions. The radiation therapy system used for irradiation creates a dose distribution that is appropriate for the shape of the target, such as a tumor, inside the patient's body, who is fixed on a patient bed called a couch.

[0003] The condition inside a patient's body changes daily, such as changes in the shape of the target or changes in gas pockets in the intestinal tract. To improve irradiation accuracy, adaptive treatment, which re-creates a treatment plan based on the patient's internal condition on the day of treatment, is becoming more common. In particular, treatment in which the treatment plan is re-planned on the day of treatment while the patient is fixed to the couch, is called online adaptive treatment.

[0004] Non-Patent Document 1 discloses a method for determining the irradiation dose in online adaptive treatment, which recreates a treatment plan on the spot according to the patient's internal condition on the day of treatment. In adaptive treatment, it is important to recreate a treatment plan so that the effect is equivalent to that of the original treatment plan that was originally created. Non-Patent Document 1 discloses a method for determining the irradiation dose by transforming the dose distribution to match the image on the day of treatment and reproducing that dose distribution as a target. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Phys. Med. Biol. 63 (2018) 085018 Summary of the Invention [Problem to be solved by the invention]

[0006] In the method of Non-Patent Document 1, the dose distribution of the original treatment plan is transformed to match the image on the day of treatment, and the irradiation parameters are optimized to realize the transformed dose distribution, thereby making it possible to replan dose-based indicators, such as the maximum and minimum doses to the target and normal organs around the target, so that they are equivalent to those of the original treatment plan.

[0007] On the other hand, since the target dose distribution is determined by the deformation, it became clear that the desired dose distribution may not be obtained depending on the deformation results.

[0008] Specifically, it may result in a dose distribution with a narrow high-dose region near the target, which ensures robustness against positional deviations, or a dose distribution with a steep dose gradient that is difficult to achieve by optimizing irradiation parameters. If the desired target dose distribution cannot be obtained, the number of optimization iterations may increase, which may increase the time required for replanning. Further improvements are needed to further reduce the burden on patients.

[0009] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a radiation therapy system that can shorten the time required for re-planning adaptive therapy compared to conventional systems. [Means for solving the problem]

[0010] The present invention includes a plurality of means for solving the above-mentioned problems, and one example thereof is a radiation therapy system for irradiating radiation, which performs a first calculation to create a new image based on an image at the time of treatment planning and another image that is newer than the image at the time of treatment planning, performs a second calculation to create a target dose distribution based on the image at the time of treatment planning, a dose distribution, and another image that is newer than the image at the time of treatment planning, and optimizes irradiation parameters with the target dose distribution as a target, and the first calculation and the second calculation have different calculation conditions and algorithms. The first calculation and the second calculation include non-rigid registration, and the second calculation includes non-rigid registration using contour data of the target in the image at the time of treatment planning and the other image and contour data created by enlarging the contour. It is characterized by: [Effects of the Invention]

[0011] According to the present invention, adaptive therapy can be shortened compared to the conventional art. Objects, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an overall configuration diagram of a radiotherapy system according to Example 1. FIG. [Figure 2] 1 is a schematic diagram of software used in a re-planning system for a radiation therapy system according to Example 1. FIG. [Figure 3] 1 is a flowchart showing re-planning in the radiotherapy system according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing a data flow from step S101 to step S104 in FIG. 3. [Figure 5] FIG. 1 is a diagram showing a data flow at the time of re-planning in a general radiation therapy system. [Figure 6] 10 is an example of a cross-sectional image in the body axis direction of a treatment planning image in a radiation therapy system according to an embodiment. [Figure 7] 1 is an example of a dose distribution of a treatment plan in a radiation therapy system according to an embodiment. [Figure 8] 10 is an example of a cross-sectional image in the body axis direction of a treatment planning image in a radiation therapy system according to an embodiment. [Figure 9] 10 is an example of a cross-sectional image in the body axis direction of an image on a treatment day in a radiation therapy system according to an embodiment. [Figure 10] 10 is an example of a cross-sectional image in the body axis direction of an image on a treatment day in a radiation therapy system according to an embodiment. [Figure 11] 10 is an example of a setting screen of the workflow manager 10 in the radiotherapy system according to the embodiment. [Figure 12] This is an example of the results of creating a target dose distribution in a typical radiation therapy system. [Figure 13] 10 is an example of the results of creating a target dose distribution in the radiotherapy system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the radiation therapy system of the present invention will be described below with reference to the drawings. Note that the following description and drawings are merely examples for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0014] In the drawings explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

[0015] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0016] When there are multiple components with the same or similar functions, they may be described using the same reference numeral with different subscripts. However, when there is no need to distinguish between these multiple components, the subscripts may be omitted.

[0017] Example 1 A first embodiment of the radiotherapy system of the present invention will be described with reference to FIGS. 1 to 13. FIG.

[0018] First, the overall configuration of a radiotherapy system will be described with reference to Fig. 1. Fig. 1 is an overall configuration diagram of a radiotherapy system according to a first embodiment.

[0019] As shown in FIG. 1, the radiation therapy system 1 of Example 1 includes a workflow manager 10, a patient positioning system 11, a replanning system 12, a patient QA (Quality Assurance) system 13, an imaging device 20, an imaging control device 21, an irradiation device 30, an irradiation control device 31, a rotating gantry 40, a gantry control device 41, a couch 50, and a couch control device 51.

[0020] The bed on which the patient 60 rests is called the couch 50. The couch 50 can move in the directions of three orthogonal axes and can also rotate around each axis based on commands from the couch control device 51. These movements and rotations allow the position of the target 61 to be moved to a desired position.

[0021] Based on instructions from the imaging control device 21, the imaging device 20 measures three-dimensional images of the patient 60 fixed to the couch 50 and the target 61. The three-dimensional images are CT images, cone-beam CT images, or MRI images, and will be referred to as treatment day images below.

[0022] The irradiation device 30 generates radiation used for treatment based on instructions from the irradiation control device 31. Specifically, it forms a desired dose distribution on the target 61 by controlling the energy, irradiation position, and irradiation amount of the radiation. A part of the irradiation device 30 is installed on the rotating gantry 40 and can rotate together with the rotating gantry 40. The rotating gantry 40 can be moved to a desired angle based on instructions from the gantry control device 41. By changing the angle of the rotating gantry 40, radiation can be irradiated from a desired angle.

[0023] The patient positioning system 11 calculates the amount of position correction of the patient 60 relative to the irradiation device 30 based on the CT image at the time of treatment planning (hereinafter referred to as the treatment plan image) and the treatment day image acquired by the imaging device 20. The operator 70 checks the calculation result and determines the amount of position correction. Based on the determined amount of position correction, the installation position of the couch 50 is calculated and set in the couch control device 51.

[0024] The re-planning system 12 generates a composite CT image to be used for re-planning based on the treatment plan image and the treatment day image. Furthermore, it identifies target and normal tissue regions on the composite CT image and creates their contour data. Furthermore, it optimizes radiation irradiation parameters based on the composite CT image and the contour data to create a day's plan. Furthermore, it calculates the dose distribution of the day's plan and displays it on the display device 102 of the workflow manager 10. The operator 70 checks the screen displayed on the display device 102 to determine whether or not to use the day's plan for that day's treatment.

[0025] The patient QA system 13 verifies the plan for the day, and the operator checks and approves the verification results.

[0026] The workflow manager 10 is connected to an imaging control device 21, an irradiation control device 31, a gantry control device 41, a couch control device 51, a patient positioning system 11, a replanning system 12 and a patient QA system 13, and monitors and manages the progress of the treatment workflow.

[0027] The workflow manager 10 has an input device 101 for inputting various parameters, etc., a display device 102, a memory (storage medium) 103, a database (storage medium) 104, a processing unit 105 (a control device that is a calculation element) that monitors and manages the progress of the workflow, and a communication unit 106.

[0028] The workflow manager 10 is configured from a device capable of performing various types of information processing, for example, an information processing device such as a computer.

[0029] The computing element is, for example, a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), or an FPGA (Field-Programmable Gate Array). The storage medium is, for example, a magnetic storage medium such as an HDD (Hard Disk Drive), or a semiconductor storage medium such as a RAM (Random Access Memory), a ROM (Read Only Memory), or an SSD (Solid State Drive). In addition, a combination of an optical disk such as a DVD (Digital Versatile Disk) and an optical disk drive is also used as a storage medium. Other well-known storage media such as magnetic tape media are also used as storage media.

[0030] The storage medium stores programs such as firmware. When the workflow manager 10 starts operating (for example, when the power is turned on), the programs such as firmware are read from the storage medium and executed to control the entire workflow manager 10. In addition to the programs, the storage medium also stores data necessary for each process of the workflow manager 10.

[0031] Alternatively, some of the components that make up the workflow manager 10 may be connected to each other via a LAN (Local Area Network), or may be connected to each other via a WAN (Wide Area Network) such as the Internet.

[0032] Although not shown, the various devices and systems that make up the radiation therapy system 1, such as the patient positioning system 11, are also comprised of information processing devices such as computers.

[0033] 2 is a schematic diagram of software used in the re-planning system 12 according to the embodiment. As shown in FIG. 2, the re-planning system 12 includes a contour creation module 121, a planning image creation module 122, a target dose distribution creation module 123, and an irradiation parameter optimization module 124.

[0034] Figure 3 is a flowchart for replanning. Before replanning is executed, the replanning system 12 stores pre-created treatment plan data and treatment date images input from the database 104 of the workflow manager 10. Here, the treatment plan data includes the treatment plan image, contour data at the time of treatment planning, irradiation parameters, and dose distribution data of the treatment plan.

[0035] 3, the contour creation module 121 identifies the target and normal tissue regions based on a treatment day image that is newer than the treatment planning image at the time of treatment planning, and creates their contour data (step S101). Also, contour data for creating a target dose distribution is created for the treatment planning image and the treatment day image (step S101).

[0036] Next, the planning image creation module 122 creates a composite CT image to be used for re-planning based on the treatment plan image and the treatment day image (step S102). The processing of step S102 corresponds to a first calculation for creating a new image based on the treatment plan image and the treatment day image.

[0037] Specifically, in step S102, a synthetic CT image is generated by deforming the treatment plan image based on the treatment day image using non-rigid image registration (hereinafter referred to as DIR). The contour data generated in step S101 may be used. Here, non-rigid registration refers to generating a vector that moves the position of each pixel in the deformed image to the corresponding pixel position in the target image, and deforming the deformed image so that it matches the target image.

[0038] Next, the target dose distribution generation module 123 generates a target dose distribution for the treatment day based on the contour data for generating the target and target dose distribution and the dose distribution data of the treatment plan (step S103). The processing of step S103 corresponds to a second calculation for generating a target dose distribution based on the image at the time of treatment planning, the dose distribution, and another image newer than the treatment planning image.

[0039] Specifically, in step S103, the treatment plan image is deformed relative to the treatment day image by DIR based on the contour data for creating the target dose distribution, and a deformation vector field (DVF) is calculated, which is the amount of deformation. Furthermore, the dose distribution of the treatment plan is deformed based on this DVF to calculate the target dose distribution. Here, the deformation calculation for calculating the target dose distribution in step S103 uses calculation conditions and algorithms different from those used in the deformation calculation in step S102.

[0040] Next, the irradiation parameter optimization module 124 performs optimization calculations to determine irradiation parameters that achieve the target dose distribution based on the composite CT image generated in step S102 and the contour data generated in step S103 (step S104). Furthermore, the target dose distribution when irradiation is performed using the irradiation parameters obtained by the optimization calculations is calculated and displayed on the display device 102 of the workflow manager 10 (step S104).

[0041] Thereafter, the operator 70 checks the target dose distribution displayed on the display device 102 of the workflow manager 10 and determines whether it is applicable to the treatment on that day (step S105). If it is determined to be inapplicable in step S105, the optimization conditions are changed and step S104 is executed again. If it is determined to be applicable, the replanning is completed and the plan for that day is verified by patient QA.

[0042] Figure 4 shows the data flow from step S101 to step S104. This embodiment is characterized in that the target dose distribution and the composite CT image are created using different deformation calculations (first calculation and second calculation). For comparison, Figure 5 shows the data flow during re-planning using a general radiation therapy system.

[0043] Next, a method for creating contour data for creating a target dose distribution and a method for creating a target dose distribution will be described with reference to FIGS.

[0044] 6 shows an example of a cross-sectional image in the body axis direction of a treatment planning image. A target 61A is displayed within a body contour 62.

[0045] 7 shows an example of the dose distribution of a treatment plan. A high-dose region 63 is formed with a certain width outside the target 61A, and a low-dose region 64 is formed around it. By extending the high-dose region 63 to the outside of the target 61A, it is possible to prevent a decrease in the dose delivered to the target 61A even if the position of the target 61A changes during treatment.

[0046] Figure 8 shows an example of a cross-sectional image in the body axis direction of a treatment planning image. An enlarged contour 65A, which is an enlarged target 61A, is displayed as contour data for creating a target dose distribution. The enlarged contour 65A is created by enlarging the target 61A three-dimensionally and isotropically according to a preset enlargement amount. As shown in Figure 8, multiple enlarged contours 65A can also be created by changing the enlargement amount.

[0047] Figure 9 shows an example of a cross-sectional image in the body axis direction of the image on the day of treatment. Target 61B is displayed within body contour 62. Figure 9 simulates a situation in which target 61B on the day of treatment has shrunk compared to target 61A at the time of treatment planning, and a partial depression has occurred.

[0048] Figure 10 shows an example of a cross-sectional image in the body axis direction of the image on the day of treatment. A contour 65B obtained by enlarging the target 61B is displayed as contour data for creating the target dose distribution. The contour 65B is created by enlarging the target 61B three-dimensionally and isotropically according to a preset enlargement amount. Also, as shown in Figure 10, multiple contours 65B can be created by changing the enlargement amount. The number of contours 65B to be created and the enlargement amount are the same as those used to create the enlarged contour 65A.

[0049] When creating the target dose distribution in step S103, the treatment plan image is transformed with respect to the treatment day image by DIR based on the target and contour data for creating the target dose distribution, and the DVF, which is the transformation amount, is calculated. Specifically, the DVF is calculated by expanding and transforming the target 61A to match the target 61B, the expanded contour 65A1 to match the expanded contour 65B1, and the expanded contour 65A2 to match the expanded contour 65B2. The dose distribution of the treatment plan is transformed based on this DVF, and the target dose distribution on the treatment day is calculated.

[0050] 11 shows an example of a setting screen of the workflow manager 10. The operator 70 operates the workflow manager 10 to specify the number of enlarged contours to be created and the enlargement interval.

[0051] Next, the effects of this embodiment will be described.

[0052] For comparison, we first explain the conventional method for creating the target dose distribution. In the conventional method, the DVF is calculated by deforming the treatment plan image, the treatment day image, and the contour data of the target and normal tissue, and the dose distribution of the treatment plan is then deformed using the DVF (see Figure 5).

[0053] Figure 12 shows an example of the results of creating a target dose distribution using a conventional method. If the target 61B on the treatment day is smaller than the target 61A in the treatment plan and has a partial depression, the high-dose region 63 of the target dose distribution may be closer to the target 61B. In this case, the high-dose region 63 outside the target 61B becomes narrower, potentially reducing robustness to misalignment and errors in the composite CT image. Furthermore, it is possible to obtain a target dose distribution that is difficult to achieve through optimization of irradiation parameters, such as a high-dose region 63 with a depression or a dose distribution with a steep dose gradient. In this case, the difficult-to-achieve dose distribution may require an increased number of optimization iterations, potentially increasing the time required for replanning.

[0054] 13 shows an example of the results of creating a target dose distribution using the method of this embodiment. In creating the target dose distribution using this embodiment, the DVF is calculated by deforming based on the expanded contour 65, and the dose distribution in the treatment plan is then deformed using the DVF to obtain the target dose distribution on the treatment day. Therefore, by deforming the dose distribution while maintaining the spread of the high-dose region 63 outside the target 61, the proximity of the high-dose region 63 to the target 61B, the concavity of the dose distribution, and the steep dose gradient are alleviated. As a result, a target dose distribution that is easy to achieve is obtained, reducing the possibility of an increase in optimization time and shortening the time required for replanning during adaptive treatment compared to conventional methods.

[0055] <Example 2> Second Embodiment A radiotherapy system according to a second embodiment of the present invention will be described.

[0056] The difference between the radiotherapy system of this embodiment and the radiotherapy system 1 of embodiment 1 is the method of creating the enlarged contour 65. In this embodiment, the enlarged contour 65 is created by the following two procedures (1) and (2).

[0057] (1) The contours in the depth direction as viewed from each radiation irradiation direction are enlarged using the water equivalent path length. In contrast, the contours in the direction lateral to each radiation irradiation direction are enlarged using the actual distance. This creates a partially enlarged contour for each radiation irradiation direction.

[0058] (2) An enlarged outline is created by logically summing the partial enlarged outlines for each irradiation direction.

[0059] The other configurations and operations are substantially the same as those of the radiotherapy system of the first embodiment, and the details are omitted here.

[0060] Next, the effects of this embodiment will be described.

[0061] In particle beam therapy for the lungs or the like, if there is a low-density area outside the target 61, it is known that the high-dose area 63 near the outside of the target according to the treatment plan will not be equidistant from the target 61. Specifically, the range of the high-dose area 63 changes depending on the water-equivalent path length as viewed from the irradiation direction.

[0062] In this embodiment, the expanded contour 65A is created based on the water equivalent path length as viewed from the irradiation direction. This makes it easy to make the shape of the expanded contour 65A closer to the shape of the high-dose region 63 in the treatment plan. This makes it easy to create a target dose distribution that maintains the spread of the high-dose region 63 outside the target 61. As a result, a target dose distribution that is easy to achieve can be obtained, and the possibility of an increase in optimization time can be further reduced.

[0063] Example 3 A radiotherapy system according to a third embodiment of the present invention will be described.

[0064] The difference between the radiation therapy system of this embodiment and the radiation therapy systems of the other embodiments is the method of creating the enlarged contour 65. In the radiation therapy system of this embodiment, the enlarged contour 65 created in the radiation therapy system of embodiment 1 or embodiment 2 is corrected by performing a filter process on the enlarged contour 65.

[0065] Specifically, an image filter such as a Gaussian filter is applied to a three-dimensional image in which the inside and outside of the enlarged contour 65 are replaced with binary values. The enlarged contour 65 is created by regarding voxels in the obtained three-dimensional image that have a pixel value equal to or greater than a predetermined value as the internal region of the enlarged contour 65.

[0066] Next, the effects of this embodiment will be described. In this embodiment, an image filter is applied to create the enlarged contour 65. Therefore, the concavity of the enlarged contour 65 is reduced. As a result, a target dose distribution that is easy to achieve can be obtained, further reducing the possibility of an increase in optimization time.

[0067] Example 4 A radiotherapy system according to a fourth embodiment of the present invention will be described.

[0068] The difference between the radiation therapy system of this embodiment and the radiation therapy systems of the other embodiments is the method of creating a target dose distribution. In the radiation therapy system of this embodiment, an image filter such as a Gaussian filter is applied to the created target dose distribution in the radiation therapy systems of embodiments 1 to 3 to modify the target dose distribution, and the modified target dose distribution is used.

[0069] Next, the effects of this embodiment will be described. In this embodiment, an image filter is applied to create a target dose distribution. Therefore, depressions and steep dose gradients in the target dose distribution are reduced. As a result, a target dose distribution that is easy to achieve is obtained, further reducing the possibility of an increase in optimization time.

[0070] <Example 5> A radiotherapy system according to a fifth embodiment of the present invention will be described.

[0071] The difference between the radiation therapy system of this embodiment and the radiation therapy systems of other embodiments is the method of creating the target dose distribution. In the radiation therapy system of this embodiment, when creating the target dose distribution, the enlarged contour 65 is not used, and a penalty term is added to the objective function of the transformation calculation to reduce depressions and steep dose gradients in the target dose distribution. Specifically, a penalty term is added for the dose gradient after transformation and for depressions in the dose distribution in the depth direction as viewed from the irradiation direction.

[0072] Next, the effects of this embodiment will be described. In this embodiment, a target dose distribution is created by a deformation calculation in which a penalty term is added to the objective function to reduce the depressions and steep dose gradients in the target dose distribution. Therefore, depressions and steep dose gradients in the target dose distribution are reduced. As a result, a target dose distribution that is easy to achieve is obtained, further reducing the possibility of an increase in optimization time.

[0073] <Other> It should be noted that the present invention is not limited to the above-described embodiment, and includes various modifications. The above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations.

[0074] The above-described configurations, functions, processing units, processing means, etc. may be partially or entirely implemented in hardware, for example, by designing them as integrated circuits. The above-described configurations, functions, etc. may also be implemented in software, with a processor interpreting and executing a program that implements each function. Information such as the programs, tables, and files that implement each function can be stored in memory, a storage device such as a hard disk or SSD, or a storage medium such as an IC card, SD card, or DVD.

[0075] In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and do not necessarily show all the control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected. [Explanation of symbols]

[0076] 1: Radiation therapy system 10: Workflow Manager 11: Patient positioning system 12: Re-planning system 13: Patient QA System 20: Imaging device 21: Imaging control device 30: Irradiation device 31: Irradiation control device 40: Rotating gantry 41: Gantry control device 50: Couch 51: Couch control device 60:Patient 61: Target 61A: Target on treatment planning image 61B: Target on treatment day image 62:Body contour 63: High dose area 64: Low dose area 65A, 65A1, 65A2: Enlarged outline of target on treatment planning image 65B, 65B1, 65B2: Enlarged outline of target on treatment day image 70: Operator 101: Input device 102:Display device 103: Memory (storage medium) 104: Database (storage medium) 105: Processing unit 106: Communication equipment 121: Contour creation module 122: Planning image creation module 123: Target dose distribution generation module 124: Irradiation parameter optimization module

Claims

1. A radiation therapy system for irradiating radiation, comprising: performing a first calculation to generate a new image based on the treatment planning image and another image that is more recent than the treatment planning image; performing a second calculation to generate a target dose distribution based on the treatment planning image, the dose distribution, and another image that is newer than the treatment planning image; optimizing irradiation parameters to achieve the target dose distribution; The first calculation and the second calculation have different calculation conditions and algorithms, the first calculation and the second calculation include non-rigid registration; The second calculation includes non-rigid registration using contour data of the target in the treatment planning image and the other image and contour data created by enlarging the contour. A radiation therapy system characterized by:

2. 2. The radiation therapy system according to claim 1, The contour data is created by enlarging the contour in accordance with the water equivalent path length as viewed from the irradiation direction of the radiation. A radiation therapy system characterized by:

3. 2. The radiation therapy system according to claim 1, Applying an image filter to the contour data to generate modified contour data, and using the modified contour data A radiation therapy system characterized by:

4. 2. The radiation therapy system according to claim 1, Applying an image filter to the target dose distribution to create a modified target dose distribution, and using the modified target dose distribution. A radiation therapy system characterized by:

5. A radiation therapy system for irradiating radiation, comprising: performing a first calculation to generate a new image based on the treatment planning image and another image that is more recent than the treatment planning image; performing a second calculation to generate a target dose distribution based on the treatment planning image, the dose distribution, and another image that is newer than the treatment planning image; optimizing irradiation parameters to achieve the target dose distribution; The first calculation and the second calculation have different calculation conditions and algorithms, the first calculation and the second calculation include non-rigid registration; The second calculation includes, in the objective function of the non-rigid registration, a penalty term for the dose gradient after deformation and a penalty term for the concavity of the dose distribution in the depth direction as viewed from the irradiation direction of the radiation. A radiation therapy system characterized by:

6. A radiation therapy system for irradiating radiation, comprising: performing a first calculation to generate a new image based on the treatment planning image and another image that is more recent than the treatment planning image; performing a second calculation to generate a target dose distribution based on the treatment planning image, the dose distribution, and another image that is newer than the treatment planning image; optimizing irradiation parameters to achieve the target dose distribution; the first calculation and the second calculation include non-rigid registration; The non-rigid registration of the first calculation and the non-rigid registration of the second calculation use different calculation conditions or algorithms. A radiation therapy system characterized by:

Images